A small patch has been released for Penumbra: Requiem, you can get it here. The patch will improve performance in some levels as well as correcting various minor errors, for slightly more details see the support article.

It won't work to load a saved game of level 9, you will need to load a save from level 8 or use this tip http://frictionalgames.com/forum/showthr...p?tid=2469 to start directly in level 9 as a new game. It is because a save will use the old level files even with the update installed.

Can you verify that the files have been replaced properly? Go to the installation location and navigate down to "Penumbra Black Plague\redist\expansion01\maps" and check if level09.dae and level09.hps have modified dates that are in September.

What CPU(Model and speed), what Graphics card and what OS are you running?

Running any programs in the background, forcing any settings with the graphics card control panel or using any sort of non-standard Windows program(for example special skin program to create fancy effects) that is likely to interfere?